1. Field of the Invention
This invention relates to improvements in needle looms, and more particularly, to means for stopping the operation of the loom when a fabric tape is improperly wound on a take-up roll or wraps around a pull roll to an undue extent, so the condition can be corrected before an end of the tape breaks requiring rethreading and down-time of the loom, or before tape becomes wrapped around rolls to the extent that mechanical damage to the loom results.
2. Description of the Prior Art
Needle looms differ from shuttle looms in that the weft is inserted by a needle and knitted in a chain stitch along one side of a tape fabric including a plurality of warp threads in order that the weft can subsequently be removed after treatment of the fabric, e.g., by coloring, and the fabric unravelled to provide a yarn with intermittent coloring or splotches which is then rewoven. Such a process is commonly referred to as "weave-de-weave" and is described in detail in U.S. Pat. No. 3,605,225.
As a consequence, a shuttle loom operates at much slower speeds than a needle loom reversing direction through opposite sheds of the fabric so that the filling or weft is locked in on both edges of the tape by its return wrap around the selvage ends. Because of the high throughput of the needle loom, mechanical damage to the rollers and gear train of the loom and the fabric tape frequently occurs when an exit roller becomes wrapped by too slack a fabric tape being drawn away from the machine.
In the preparation of tapes for the weave-de-weave process, this problem is compounded by the wide pick spacing. A pick is one pass of the weft through the warp. This spacing is normally 0.5 - 2.0 inches, which reduces filling usage and also facilitates removal of the weft during deleasing, subsequent to coloring. Because of the high warp to filling ratio, the throughput of tape through a weave-de-weave loom is extremely high. That is, for every pick of filling across the tape, the tape advances through the machine 0.5 to 2.0 inches instead of distances on the order of 1/32 inch as in ordinary tape looms. Tape delivery through the loom can be as high as 50 - 75 yards per minute. At this high speed it is essential to have stop motions fitted to prevent wraps on rollers, since the greater throughput equates to larger roller wraps in much shorter time periods. There is also a need for a stop motion device that will shut off the machine before a warp end breaks, thereby reducing rethreading down-time.
U.S. Pat. Nos. 2,771,911 and 3,703,914 illustrates two forms of stop motion devices which have been used on looms heretofore. In U.S. Pat. No. 2,771,991, the stop motion includes a toggle switch having a free end pivotally disposed between a fabric guide roller and a sand roll about which the fabric is wrapped. Should the fabric wind completely about the sand roll, the toggle switch end in the nip between the rollers is contacted and the switch closed to stop the operation of the loom. Similarly, in U.S. Pat. No. 3,703,914, a pivoted bell-crank lever in the nip is pivoted by the fabric to close a circuit to stop the loom if improper winding in the nip is detected. However, these prior art stop motion devices do not have any degree of adjustability which is necessary in the higher speed narrower width, needle loom because of the increased throughput and variation in pick spacing.